1. Field of the Invention
The present invention relates generally to devices for pumping liquid, and more particularly to a liquid pumping device that is activated by pressurized gas, and which includes an input chamber and an output chamber with valves to control both liquid and gas flow.
2. Description of the Prior Art
In nearly every fluid transfer application it is necessary to provide a pump to provide the motive force to move the liquid through a liquid supply line. With the exception of gravitational systems and siphon systems, the utilization of liquid pumps is a necessity and many types of pumps have been developed throughout history. Many of the pumps are powered by rotating or reciprocating motorized devices which tend to create a vibration or pulsation in the pumped liquid and the systems that utilize such pumps. For many applications the vibration and pressure pulsation of such pumps is insignificant and such pumps provide adequate performance.
However, many liquid transfer applications involve liquids having a delicate chemical make-up and chemical processes that are adversely affected by the pulsation and vibration of pumped liquid. For such applications it is necessary to utilize a pump that does not create pulsation and vibration of the pumped fluid. Additionally, many precise chemical processes require strict control of the flow rate of the pumped liquid, and prior art pumps that induce pulsation and vibration within the pumped fluids have difficulty meeting such flow rate constraints. Semiconductor fabrication processes are one such application in which ever stricter constraints on liquid pumping parameters continue to be developed. In many particular applications within the semiconductor fabrication industry pulsation and vibration of pumped chemicals adversely affects the delicate chemical balance of processing liquids as well as the chemical reactions of the processing liquids with the semiconductor substrates in the various fabrication steps.
A need therefore exists for pumps that move liquids without subjecting the liquids to pulsation and vibration, while providing tight control of the delivery pressure of the pumped liquids. The present invention, in its various embodiments disclosed herein, provides a pump system that utilizes pressurized gas to provide the motive force to continuously pump liquids through liquid flow lines. The pulsation and vibration created by the prior art pumping systems is eliminated and a strict control of pumped liquid delivery pressure is obtained.
The fluid pump of the present invention includes an upper enclosure for holding fluid (typically a liquid) from a fluid input source, and a lower enclosure for outputting the fluid to an output line. A first valve (A) controls the fluid input flow into the upper enclosure. A second valve (B) is engaged in a line between the upper enclosure and the lower enclosure to control the fluid flow from the upper enclosure to the lower enclosure. A second fluid input line is engaged to the lower enclosure to input a second fluid (typically a pressurized gas) into the lower enclosure, and a third valve (D) is engaged in a line between the lower enclosure and upper enclosure to control the flow of the second fluid into the second enclosure. A fourth valve (C) is engaged in a fluid output line to control the flow of the second fluid out of the upper enclosure. In the preferred embodiments, each of valves A, B, C and D is controlled by an automated pump system controller. Various embodiments of the present invention include further valves and check valves to provide improved control in the system. The preferred embodiment of the dual chamber pump operates by outputting the liquid from the lower enclosure under a constant, controlled gas pressure. When the liquid level in the lower enclosure is low, the lower enclosure is filled with liquid from the upper enclosure. To accomplish this, the upper enclosure is pressurized to the same pressure as the lower enclosure, and because the upper enclosure is disposed above the enclosure, the gravitational head causes the liquid in the upper enclosure to flow into the lower enclosure. The upper enclosure is filled during the pump cycle in which the lower enclosure is outputting liquid. The pump thus has a repeatable cycle, although the gas pressure in the lower enclosure remains constant and liquid is constantly output from the pump at a controlled pressure.
It is an advantage of the present invention that a liquid pump is provided which pumps liquid without vibration and pulsation.
It is another advantage of the present invention that a liquid pump is provided which pumps liquid at a constant pressure.
It is a further advantage of the present invention that a liquid pump is provided having an upper enclosure and a lower enclosure, such that liquid flowing from the lower enclosure can be replaced by liquid from the upper chamber without cessation in the liquid output flow.
These and other features and advantages of the present invention will become apparent to those skilled in the art upon review of the following detailed description which makes reference to the several figures of the drawing.